Jointed Rush

A widely distributed and very variable species, known to have: (i) several ecotypes (Clapham et al, Fl.Brit. Isles 990, 1962); (ii) larger forms with 80 chromosomes and up to 18 flowers in each head; (iii) and hybrid, with sterile capsules and usually 3-6 flowers in each head.

Juncus articulatus hybridizes with J. brevicaudatus (= J. ´ xfulvescens Fernald), J. alpinus (= J. ´ xalpiniformis Fernald), J. nodosus, and J. canadensis.

Juncus articulatus var. obtusatus Engelmann appears to be intermediate with J. alpinus. It has spreading inflorescence branches but obtuse inner tepals. This may represent a backcross with J. alpinus. Recent evidence suggests that J. alpinus is a polyploid species with J. articulatus as one of its parents.

Perennial, shortly rhizomatous, greenish herb, (10-) 15-50 (-80) cm tall, erect to almost prostrate, sometimes rooting from the lower nodes, non-stoloniferaus; stem terete, faintly sulcate with 2-6 cauline leaves. Leaves shorter than stem linear transversely 15-25 septate-nodose, subterete, green, usually 1-2 mm broad; basal sheaths usually brownish, auricled. Inflorescence terminal, often richly and somewhat dichotomously branched, with many shortly stalked heads, each consisting of (4)6-10(-12) flowers, 5-10 mm across; lowest bract erect, usually c. half as long as the inflorescence, leafy. Flowers (2-)2.5-3 mm long, brownish to greenish, sessile; perianth segments lanceolate, acute inner subobtuse with broad whitish margins. Stamens 6, much shorter than the perianth, with anthers c. as long as the filaments. Capsules 34 mm long, 1.5-2 mm broad, oblong-ovoid or ellipsoid, usually contracted abruptly into a short beak, conspicuously exceeding the perianth, brownish to greenish, often lustrous, many seeded (3040); seeds c. 0.4(-0.5) mm long, ovoid or ellipsoid, brownish 2n=80.

Herbs, perennial, rhizomatous to nearly cespitose, 0.5--6(--10) dm. Rhizomes 2--3 mm diam., not swollen. Culms erect to decumbent (and floating), terete, 1--3 mm diam., smooth. Cataphylls 1, maroon to straw-colored, apex acute to obtuse. Leaves: basal 0--2, cauline (1--)3--6; auricles 0.5--1 mm, apex rounded, scarious; blade green to straw-colored, terete, 3.5--12 cm x 0.5--1.1 mm. Inflorescences terminal panicles of 3--30(--50) heads, 3.5--8 cm, branches spreading; primary bract erect; heads 3--10-flowered, obpyramidal to hemispheric, 6--8 mm diam. Flowers: tepals green to straw-colored or dark brown, ovate to lanceolate, 1.8--3 mm; outer tepals with apex acute or acuminate; inner tepals with apex acute acuminate to obtuse; stamens 6, anthers equal to filament length. Capsules exserted ca. 1 mm beyond perianth, chestnut brown to dark brown, imperfectly 3-locular, ellipsoid or ovoid, 2.8--4 mm, apex acute proximal to beak, valves separating at dehiscence. Seeds obovoid, 0.5 mm, not tailed. 2n = 80.

Plants perennial, tufted or rhizome creeping, (10--)15--40(--60) cm tall. Stems terete, 0.8--1.5 mm in diam. Cataphylls absent to 2. Cauline leaves 2--6; leaf sheath auricles well developed, acute, free part ca. 2 mm, membranous; leaf blade terete or somewhat laterally compressed, 2.5--7.5(--10) cm × 0.8--1.4 mm, perfectly septate. Inflorescences usually broad; branches rigid, spreading; involucral bract erect to ascending, 0.7--3 cm; heads 5--30, hemispheric to toplike, 5--10(--15)-flowered. Perianth segments reddish brown with greenish midvein, lanceolate, 2.5--3 mm, subequal, apex acute. Stamens 6, 1/2--3/4 as long as perianth; filaments 0.7--0.9 mm; anthers oblong, 0.5--1 mm. Capsule dark brown, shiny, trigonous ovoid, 3--3.5 mm, apex sharply acute and tapered to a conspicuous tip. Seeds ovoid, 0.5--0.7 mm, reticulate. Fl. Jun--Jul, fr. Aug--Sep. 2 n = 80.

Temperate regions, W. Himalaya.

Distribution: Most of Europe, N. Africa, Central and S.W. Asia, to Pakistan and the Himalayas; eastern N. America; widely introduced reaching Australia and New Zealand.

St. Pierre and Miquelon; B.C., N.B., Nfld. and Labr. (Nfld.), N.S., Ont., Que., P.E.I.; Alaska, Ariz., Colo., Calif., Conn., Idaho, Ind., Ky., Maine, Mass., Mich., Minn., Nebr., Nev., N.H., N.J., N.Mex., N.Y., N.C., Ohio, Oreg., Pa., R.I., S.Dak., Utah, Vt., Va., Wash., W.Va.; Eurasia.

Gansu, Hebei, Henan, Hubei, Ningxia, Qinghai, Shaanxi, Shandong, Shanxi, Sichuan, Xinjiang, Xizang, Yunnan [Afghanistan, Bhutan, India, Kashmir, Mongolia, Nepal, Pakistan, Russia (E Siberia), Vietnam; Africa, Europe, North America].

2300-3800 m

Fruiting mid summer--fall.

Wet ground in ditches, lake and stream margins, and a variety of other habitats, often a calciphile; 0--3000m.

Wet meadows, sand, along rivers, edges of water along ditches; 1200--3700 m.

Juncus articulatus var. obtusatus Engelmann; J. articulatus var. stolonifer (Wohlleben) House; J. lampocarpus Ehrhart ex Hoffmann

Juncus lampocarpus Ehrhart ex Hoffmann; J. lampocarpus var. senescens Buchenau.